1. Trunnion Ball Valve

1.1 What is a Trunnion Mounted Ball Valve?

Trunnion Mounted Ball Valve is one type of ball valves, which is also called fixed ball valve. The ball of the trunnion mounted ball valve is fixed and it does not move when pressed. Trunnion Mounted Ball Valves are equipped with a floating seat. Under the action of the medium pressure, the seat will move to make the sealing ring tightly press on the sphere to ensure sealing. Bearings are usually installed on the upper and lower shafts of the sphere, and the operating torque is small, which is suitable for high pressure and large diameter valves.

1.2 Trunnion Mounted Ball Valve Assembly

The valve is usually assembled with the valve body as the reference part, in the order and method specified by the process. Before assembling, check the parts and components to avoid the parts that are not deburred and cleaned from entering the final assembly. During the assembly process, the parts should be handled with care to avoid bumping and scratching the processing personnel. The wrench used for tightening should not be too long to prevent the pre-tightening force from being too large and affecting the bolt strength. After the final assembly is realized, the control mechanism should be rotated to check whether the movement of the valve opening and closing parts is mobile and whether there is jamming.

1.3 Trunnion Ball Valve Design

The trunnion ball valve adopts the upper and lower stem fixed valve core (shaft support type) and movable sealing seat design, which is more stable in working. With the automatic compensation function, there is a great shear force and self-cleaning function when there is no gap between the two-way sealing valve seat. It is especially suitable for the on-off of fibers, suspensions with tiny solid particles, and viscous media.

1.4 Trunnion Mounted Ball Valve Characteristics and Performance

Trunnion mounted ball valves are suitable for various pipelines of medium and high pressure. They are used to cut off or connect medium in the pipeline. Different materials are selected. They can be applied to water, steam, oil, liquefied gas, natural gas, gas, nitric acid, acetic acid, oxidizing medium, urea, and other media respectively. They are widely used in the petrochemical industry, electric power, water conservancy, and other industries. The common driving modes of trunnion mounted ball valves are worm wheel drive, manual, electric, and pneumatic. Most trunnion mounted ball valves are flanged, but there are also trunnion mounted ball valves in welded form.

2.Ball Valve Floating Type

2.1 What is a Floating Ball Valve?

Floating ball valve is another type of ball valve. The ball of the floating ball valve is floating, and the valve seat is fixed. Under the action of the medium pressure, the ball can produce a certain displacement and press tightly on the sealing surface of the outlet end to ensure that the outlet end is sealed.

2.2 Floating Ball Valve Assembly

(1) Clean and check the removed parts. It is strongly recommended to replace the valve seat and valve cover gasket with a spare parts kit. 

(2)Assemble in the reverse order of disassembly. 

(3)Tighten the stem nut by using specified torque. 

(4)After installing the control mechanism, input the corresponding signal to drive the valve core to rotate by rotating the valve stem to make the valve in the open and close position. 

2.3 Floating Ball Valve Design

The floating ball valve has a simple structure and good sealing performance. However, the load of the sphere which bears the working medium is all transmitted to the outlet sealing ring. Therefore, it is necessary to consider whether the sealing ring material can withstand the working load of the sphere medium. When it is under higher pressure impact, the sphere may shift. As a result, this structure is generally used for medium and low-pressure ball valves.

2.4 Floating Ball Valve Characteristics and Performance

The overall characteristics of the ball valve floating type are small size, lightweight, simple structure, and a sphere with a free-floating function to better ensure sealing. The ball valve uses a ball with a circular through the hole as the opening and closing part, which rotates 0-90 degrees around the center of the stem under the drive of the valve stem to complete the opening and closing function. It has the characteristics of compact structure and fast switching. It can turn 90 degrees to close the valve and cut off the pipeline medium. The diameter of the spherical passage is the same as the diameter of the pipeline. The flow resistance is small and the flow capacity is large. The valve stem is downloaded, which prevents the accident of the valve stem penetration and ensures the safety of use.

Floating Ball Valve vs Trunnion

ZECO Valve is one of the professional & famous API 6D floating ball valve and trunnion ball valve manufacturers in China.

It is also important to choose a reliable Trunnion Ball Valve manufacturer & Floating Ball Valve Manufacturer.

If any inquiries, you can contact commercial@zecovalve.com

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What is a Floating Type Ball Valve?

In a floating ball valve, the ball is suspended in the flowing fluid and is kept in position by the compression of two elastomeric seats against it.

The shaft is connected at the top of the ball and allows the switch from an open to a closed position with a quarter turn movement (90 degrees).

When the shaft is moved, a load is applied to the ball which gets pressed against its seats.

This design, which is lightweight and economic, suits bore sizes up to 10 inches: above this bore size, the seats of the valve would not be able to withstand heavier and heavier balls and the valve would not operate safely and efficiently.

Floating ball valves allow a bi-directional shut-off of the flow (as the trunnion type).

How does a Floating Ball Valve work?

Floating ball valves are operated by a shaft, or stem, attached to the top of the ball that turns it 90 degrees (a quarter turn). As the ball rotates, the port is covered or uncovered by the wall of the valve body, either releasing or halting the flow of media. The stem is attached loosely enough to the ball that, as the ball rotates on its axis, the pressure of the flow pushes the ball against its downstream seat, creating a tight seal. For this reason, floating ball valves may not seal as effectively in very low pressure applications after a certain amount of seat wear has occurred. This is because there may not be enough media pressure to force the ball against the downstream seat to create a tight seal. However, in most applications downstream pressure is sufficient to maintain a tight seal long after the seats have begun to wear.

Components of Ball Valve Floating Type

The major components of a floating ball valve include:
Valve body – A pressure vessel that contains the components needed to control or shut off the flow through a pipe. It is designed to connect two or more sections of pipe or tubing to each other.
Ball – A sphere with a flow path (hole or tunnel) through the center of it and a connection point for a shaft to rotate it.
Seats – Round donut-shaped discs that form a seal between the body and ball.
Stem – A shaft that connects the internal ball to the outside of the valve to facilitate rotation of the ball.
Packing – Flexible seals that fit around the shaft and prevent the media traveling through the valve from escaping externally.
Bonnet – The part of the valve body that houses the stem and packing.
Operator or Actuator – An external device designed to rotate the stem of the valve. This can be a lever, a gear, a motor-operated gear (electric actuator), or a pneumatic/hydraulic actuator.

Types of Ball Valve  

Based on Ball Design

The most common design is the “floating ball design”. The ball is suspended in the media and held in place by two sealing rings. Some high-quality valves have a “trunnion ball design”. The ball is supported at the top and bottom to reduce the load on the valve seats.

• Floating Ball Valve – The majority of ball valves have a floating ball. The ball is supported by the valve seats.
• Trunnion Ball Valve – Valves with large diameters and high operating pressures (for example DN >100mm and 30 bar) have often a trunnion design. The ball is supported on the bottom and top to reduce the load on the seat rings. The operating torque is generally lower for trunnion valves.

The hole through the ball may have different profiles such as a full bore, reduced bore or V-shaped.

• Reduced bore Ball Valve – Most ball valves have a reduced bore. As a result, the ball valve introduces friction losses in the system. These losses are still relatively small compared to other types of valves. One-piece ball valves are almost always reduced bore.
• Full bore Ball Valve – Full bore valves have the same bore diameter as the pipe. The advantage is that there are no extra friction losses, and that the system is mechanically easier to clean (pigging). The downside is that the ball and the housing are bigger than a standard ball valve with reduced bore. The cost is therefore slightly higher, and for many applications this is not required.
• V-shaped Ball Valve – The hole in the ball or the valve seat has a “V” shaped profile. As a result, the desired flow rate can be controlled more precisely by rotating the ball. By optimizing the profile, a linear flow characteristic can be approached.

Differences between Floating Ball Valve & Trunnion Ball Valve

What are the differences between floating ball valve & trunnion ball valve. There are major 5 points.

1. Appearance of Floating Ball Valve vs Trunnion

The floating ball valve and the trunnion ball valve are easy to distinguish in appearance. If the valve body has a fixed shaft on the bottom, it must be the trunnion ball valve.

If the ball valve body has a device for injecting grease,it is basically a trunnion ball valve.However, if there is no injecting device,can we say it must be a floating ball valve? This is incorrect, because small size such as 2 “150LB trunnion ball valves are usually not filled with injecting device either.

2. Sealing surface of Trunnion vs Floating Ball Valve

As the ball of the floating ball valve is floating, so under the pressure of the medium, the floating ball will move and against the downstream seat., so the seal of the floating ball valve belongs to the single-side seal.The ball of the trunnion ball valve cannot be moved, so the two sides of the trunnion ball valve both must be sealed.

Since the sealing principle is different, the requirements of the two ball valves on the sealing surface material are different, especially the sealing surface of the floating ball valve must be able to bear the pressure caused by the floating ball.

3. Working principle of Floating vs Trunnion Ball Valve

The floating ball valve only has upper stem and the ball can have a slight displacement, so it is called floating ball valve.The trunnion ball valve ball has another stem at the bottom to fixed the position of the ball,so the ball can’t move.

The sealing of the floating ball valve is realized by the pressure of the medium, when the ball valve is closed, the floating ball is pressed against the sealing surface under the action of pressure to realize sealing.When the trunnion ball valve is closed, the ball does not produce displacement, but the floating seats will move and press against the ball under the action of the media pressure to realize sealing.

4. Application of Trunnion Ball Valve vs Floating

The floating ball valve is suitable for medium and low pressure and usually has a small diameter.The trunnion ball valve can be used in high pressure conditions and the size can be up to 60 inches.

The trunnion ball valve is a kind of double-block-and-bleed(DBB) valve, while the floating ball valve only seal the downstream side. The trunnion ball valve can block both upstream and downstream media. And when the pressure in the middle cavity is greater than the seat spring force, the seat will be pushed open to release the pressure inside the chamber to ensure safety.

5. Characteristics of Ball Valve Trunnion vs Floating

To the floating ball valves, the trunnion ball valves are usually used longer, has smaller size and easier to operate.
 
The trunnion ball valve also has the function of automatic release pressure, when the medium temperature in the valve rises and causes abnormal pressure rise, the trunnion ball valve can automatically release the pressure without a relief valve,This is very important to ensure the safety of industrial production.

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Structure of Trunnion vs Floating Ball Valve

A trunnion ball valve consists of a ball mounted on a trunnion on the bottom and joined to a stem at the top. These parts are often welded together which is why this type of valve is sometimes referred to as a trunnion ball valve or a fully welded trunnion ball valve. Given as the ball is mounted and experiences less friction and media pressure force, this valve requires less torque to operate.

A floating ball valve, on the other hand, comprises a ball linked to a stem at the top but floats freely at the bottom. It is held in place by fluid pressure and seat rings as opposed to being mounted on a trunnion. As such, it requires high torque to operate. It is, nevertheless, a reliable bi-directional shut-off valve.

Design of Trunnion vs Floating Ball Valve

The name “floating” ball refers to the fact that the ball is suspended in the flowing medium held in position by the compression of the two elastomeric seats against it. The shaft is connected to a slot at the top of the ball which allows the ball to be driven to travel through a quarter turn (90 degrees). The shaft allows for a certain amount of lateral movement of the ball that is generated from the upstream pressure acting against the ball. This small lateral movement in fact produces a load on the ball that presses it against the downstream seat. This type of ball valve design is therefore capable of bi-directional shut-off.

The trunnion ball design in effect addresses this problem where in effect the shaft, ball, and trunnion act as a single assembly that supports the ball instead of the seats, and the seats become “floating” in a kind of reversal of the “floating ball” design. Similarly, trunnion mounted ball design is also capable of bi-directional sealing.

Floating Ball Valve vs Trunnion

Floating Ball Valve

• The valve seats are fixed in the valve body
• In the closed position, the ball can move a little bit in flow direction
• The ball is pressed against the downstream seat
• The system pressure acts on the whole circular area of the ball

Big Area – Big Force

Trunnion Ball Valve

• The ball is fixed in position by trunnions (bearing) and can only rotate
• The seats can move a little bit in flow direction
• The upstream seat is pressed against the ball
• The system pressure acts on the circular ring of the upstream seat

Small Area – Small Force

Floating ball valves use the seats and body to hold the ball in place within the fluid flow path, with the force of directional flow pushing the ball against the downstream seats to produce a tight shutoff seal. Many floating ball valves are capable of flow shutoff in either direction. The ball is rotated by a shaft connected at the top which extends through the pressure enclosure of the valve for connection to a handle or automated actuator. The floating nature of the ball limits the applicability of this design to smaller valve sizes and lower pressures. At some point, the fluid pressure exerted on the ball surface can exceed the ability of the seats to hold the ball effectively in place.

Trunnion mount ball valves employ the stem shaft and, you guessed it, a trunnion to rigidly position the ball within the body. The shaft and trunnion, connected to the top and bottom of the ball, establish a vertical axis of rotation for the ball and prevent it from shifting in response to flow pressure. The trunnion is a pin that protrudes from the bottom side of the ball. It sits within a bearing shape, generally cylindrical, at the base of the body.

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